“He means for one of us to go backward in time to when the ship arrived,” said Rigg-the-killer. “He means for us to keep making little jumps into the past, following your path moment by moment, backward along with this ship as it slammed into Garden. I mean, as it unslams, backing out of this hole and up into space, backward and backward until it gets to Earth. Until we get to the point where you launched on this voyage.”

“This ship was built in space,” said Ram Odin. “It never was on Earth.”

“We go back to when it was built,” said Rigg Noxon. “Then we follow someone else’s path off the ship.”

“If you can even do that,” said Ram Odin, “what’s the point? Why not go back with the Visitors as the other Rigg suggested and then jump back in time?”

“There are some key differences,” said Rigg Noxon. “First, we don’t have to spend the voyage in hiding—not the way we would by slicing time on the Visitors’ ship.”

Rigg-the-killer was nodding. “And we’ll have the jewels,” he said, holding up the bag of jewels that gave them the ability to control the ships’ computers—and stored all the information the computers had gathered in the meantime.

Ram Odin looked at the jewels. “Each time you jump backward,” said Ram Odin, “the ships’ computers and the expendables will be sensing these things for the first time.”

“And each time,” said Rigg Noxon, “it will give them a complete account of everything that’s been learned in the eleven millennia of history on Garden.”

“So they can take preventive measures and cause us all not to exist?” asked Ram Odin.

“They wouldn’t cause us not to exist,” said Rigg-the-killer. “Preservation of causality and all that. But yes, it might cause them to prevent the terraforming of Garden in the first place. What about that?” he asked Rigg Noxon. “Do we leave the ­jewels behind? If we do, the ship will process us as stowaways and have the expendables put us into stasis or just kill us.”

Rigg Noxon shook his head. “No. Remember what Umbo learned in his reading in the library in Odinfold? The Odinfolders—or the mice, who can tell?—worked out the math of what happened in the jump. It didn’t just create nineteen copies of the ship and all the humans and machinery on it. It also made either one or nineteen other copies that moved exactly backward in time.”